In recent years, multi-window systems which simultaneously present a plurality of windows as a user interface (UI) of an operating system (OS) which provides an execution environment of an application have been widespread.
Also, a device to be used as the execution environment of the application in recent years is not limited to a so-called personal computer (PC). Specific examples of the device include a portable terminal such as a smartphone or a tablet, a wearable terminal, a projector which projects information onto a wall surface or the like, a tabletop display, etc., and a size or a form of use of the device are diverse.